Coronal Responses to Explosive Events

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Coronal Responses to Explosive Events
Adria C. Updike
Amy Winebarger and Kathy Reeves, Center for
Astrophysics
Smith College / Harvard-Smithsonian Center for
Astrophysics
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(No Transcript)
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MDI photosphere T 5800 K EIT 304 Å T 60000
80000 K EIT 195Å T 1.5 million K EIT
171Å T 1 million K
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Coronal Heating
insert graphic from mariska book
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Coronal Heating
Solar Surface 5800 K Chromosphere 25000
K Transition Region Corona 106 K
Ruled out Radiation Convection
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Coronal Heating
Explosive Events 1024 to 1027 ergs 2,000
km Large Solar Flares 1028 to 1032 ergs 10 Mm
Insert magnetic reconnection graphic
www.nasa.gov
This image of coronal loops over the eastern limb
of the Sun was taken in the TRACE 171 Å pass
band, characteristic of plasma at 1 MK, on
November 6, 1999, at 0230 UT. The image was
rotated over 90 degrees.
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Explosive Events
1024 to 1027 ergs 2,000 km occur in Transition
Region at 100,000 K heated to coronal
temperatures?
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TRACE
Transition Region and Coronal Explorer
Observes 171 Å, 195 Å, 284 Å, 1600 Å, 1550 Å,
and 1216 Å.
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images taken May 13, 1999
1600 Å
near temperature minimum 104 K
171 Å
near temperature maximum 106 K
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SUMER
Solar Ultraviolet Measurements of Emitted
Radiation
Observed in the C IV line at 1548 Å and in the Ne
VIII line at 1540 Å.
Insert SUMER spectra from movie
Data set from May 13, 1999 from 13114.47 UT to
13336.0 UT
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Insert SUMER spectra
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Selection Criteria
profiles with greater than 500 counts average
width of C IV profile 3.3 pixels2 0.4 pixels2
average width of Ne VIII profile 4.0 pixels2
0.5 pixels2 A statistically significant event
has greater than 500 counts and is 3 s above
either average skewness or average width.
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TRACE movie
The line moving across the TRACE images marks the
position of the SUMER slit at the displayed time.
The time is the difference in the SUMER slit
time and the time of the first TRACE image.
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C IV contour map
High skewness in green, high width in red.
Created by smoothing over original contour maps.
Areas of SUMER events plotted on TRACE images.
Areas of high skewness tend to follow the coronal
loop, while the high width is concentrated at the
foot points.
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Ne VIII contour map
The high skewness is represented by light blue,
and the high width is yellow. The Ne VIII
follows the magnetic foot points more closely
than the C IV map did.
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Light Curves
We selected a small contoured area from the
figure below and averaged the number of counts in
this area as a function of time.
Area one x1 329 x2 331 y1 139 y2
140 Area two x1 305 x2 308 y1 137 y2
140 Area three x1 310 x2 312 y1 58
y2 60 Area four x1 280 x2 282 y1 70
y2 72
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Light Curves
Four light curves from TRACE 171 Å data, May 13,
1999. DN/s. The error is DN/sqrt(11).
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Light Curves
To quantify our results, we compared the maximum
short term (lt5 min) fluctuation in TRACE pixels
above event regions to normal fluctuations
observed over areas that did not show explosive
event characteristics during the SUMER scan.
The fluctuation is defined as the difference
between the minimum and maximum points on the
light curve.
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Global Birthrate
number of new events occurring each second
C IV 2108 events s-1 Ne VIII 335 events s-1
No number of observed events t total
observation time Asun surface area of the sun
that can be considered an
active region Aslit deprojected area of SUMER
slit on sun
Previous Results 753 events s-1 (Brueckner
and Bartoe) 600 events s-1 (Dere, Brueckner
and Bartoe)
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Conclusions
We found that the typical fluctuation for both
events and non-events is 1.5 DN/s. However,
while the non-events became nearly non-existant
after a fluctuation of 2.5 DN/s, the events
continued out to more than 20 DN/s. This
indicates a great amount of activity taking place
in the regions identified as events. By
constraining our time scale to 5 minutes, we
determined that 35 of our events had greater
than 3 s above non-events. We witnessed a
coronal response in TRACE to an explosive event
in SUMER 35 of the time. Explosive events can
contribute 10 of the energy required to heat the
solar corona. It is not clear whether the
explosive events are directly related to the
coronal response, or if they are both separate
responses to reconnection.